Internal combustion engine with auxiliary piston



May 24, 1938 H. BUCHWALDER INTERNAL COMBUSTION ENGINE WITH AUXILIARY PISTON Filed April 19, 1957 Patented May 24, 1938 UNITED STATES PATENT QFFHCE INTERNAL CORIBUSTION ENGINE l/VITH AUXILIARY PISTON land Application April 19, 1937, Serial No. 137,861 In Switzerland May 6, 1936 9 Claims.

This invention relates to internal combustion engines, and more particularly to an improvement in engines of the type employing main and auxiliary pistons.

In motors of this type heretofore used the auxiliary piston usually remains stationary during the operation of the main piston, and, therefore, it is impossible to obtain maximum efiiciency in operation.

Accordingly, the present invention has primarily in view a motor in which the auxiliary piston is compelled to move in definite relation to the main piston, both pistons operating in conjunction with intake and exhaust ports in the cylinder serve as valves to perform the functions of a two cycle engine. In that connection it may be pointed out that the double stroke of the main piston corresponds with two double strokes of the auxiliary piston, one of the latter having a greater amplitude than the other.

A further object of the invention is to provide novel means for mounting and operating the auxiliary piston, said means being driven by the main crank shaft of the motor.

In the accompanying drawing is illustrated diagrammatically and solely by way of example, one form of construction of the subject of the invention.

Fig. 1 is a diagram of the operation of the engine.

Figs. 2 to 5 show four specific positions of the piston and of the movable slide.

Figure 6 is a diagrammatic View illustrating a modification of the invention.

Figs. 2 to 5 show a method of obtaining the necessary desmodromic connection necessary between the movements of the main piston and those of the auxiliary piston. In these figures the cylinder is indicated at 5, the main piston at 6 and the auxiliary piston at I. Fig. 2 corresponds to the position 0 of the diagram in Fig. 1, Fig. 3 to the position d, Fig. 4 to the position e and Fig. 5 to the position 1.

At 8 there is located the crankshaft driven by the piston 6 and the connecting rod 9 in the direction of the arrow [0.

The auxiliary piston l is attached to one end ll of a tumbler l2, to the free end l3 of which a connecting rod [4, in desmodromic connection with the crankshaft, communicates an oscillatory movement. This movement is produced by the crank I5 driven by a chain IS in such a manner as to carry out two revolutions while the crankshaft carries out one.

The pivot ll of the tumbler is movable as it is located on a crank driven from the crank [5 by a chain is, in such a manner as to turn at the same speed as the crankshaft. For this reason the distance between the pivot l! and the shaft 8 is variable, the variation being oscillatory and of the same frequency as the to and fro movement of the piston.

In the diagram of Fig. 1, the curve a represents a double stroke of the piston, it extending consequently throughout a complete revolution of the crankshaft, included between 0 and 360 of the axis of the abscissae of the curve. The upper dead point of the piston is located at 0 and 360 respectively, while the lower dead point is located at The curve I) shows the corresponding movements of the auxiliary piston, which, as shown, carries out two double strokes whilst the piston carries out one, the first of these double strokes having a relatively small amplitude, in the neighbourhood of half the maximum stroke of the piston, whilst the other of these double strokes has an amplitude which is larger than the maximum stroke of the piston.

Opposite the points 0, d, e, f of the axis of the abscissae there have been drawn lines parallel to 1 the axis of the ordinates, these lines indicating the particularly important positions of the memiers of the engine.

Finally at the upper part of the diagram is shown the position of an inlet port and in the lower portion the position of an exhaust port 2.

There will now be described the operation of an engine according to the invention, assuming that its piston and the auxiliary piston move in accordance with the curves a, b and in a cylinder provided with ports at I and 2.

The space included between the piston 6 and the slide 1 is assumed to be filled with a highly compressed air-fuel mixture which has entered through port while ignition takes place approximately at c an ignition device being located. at this point, where the compression is extremely high as the main piston and auxiliary piston are not far apart. This point is located slightly beyond the upper dead point of the piston so that the explosion will drive the latter towards its lower dead point during an expansion period extending from c to cl. During this period the auxiliary piston rises and, according to the method of connection. adopted between. it and the piston, it is also capable of transmitting the driving force from the exploded charge to the engine shaft 8.

Having reached the point at the piston uncovers the exhaust port 2 which remains uncovered until the point e is reached. As the auxiliary piston then approaches the main piston 6 rapidly, as shown in Figures 3 and i there is produced between at and e a complete scavenging of the combustion gases, as indicated diagrammatically by the arrow 3. At 6 the piston and the slide are again at a point at which they nearly touch so that the quantity of combustion gases capable of remaining in the combustion chamber may be regarded as practically nil. and f the main piston and the auxiliary piston again separate from one another as shown in Fig. 4 to Fig. 5, suction takes place, the gases enter ing from inlet port I when the piston 6 has moved to uncover the port, as indicated by the arrow 4, through the port i which is now exposed by the movable part of the slide.

Between 1 and c compression occurs, this being the starting point referred to at the beginning of this description.

It may be mentioned that if the exhaust port is exposed at each stroke of the main piston 6, the inlet port is only exposed every two strokes of'the auxiliary piston i when this carries out its movement of large amplitude and at the upper dead point relatively to the crankshaft.

It may also he mentioned that the engine of which the operation has been described, functions as a two-stroke cycle engine as an explosion is produced at each double stroke of the piston, but that it has the complete cycle of a fourstroke engine, that is to say suction, compression, expansion and exhaust.

When passing from the position in Fig. 2 to that in Fig. 3, that is to say from c to d in the diagram, it will be seen that the piston 6 has approached its lower dead point while the crank which drives the connecting rod I 4 is nearly in its lowest position, therefore the auxiliary piston is near its upper dead point, indicated at IS in the diagram. This dead point is not the highest which the auxiliary piston l is capable of reaching as the movement of rotation of the pivot ll causes the latter at this moment to approach the shaft 8.

When passing from the position described to that in Fig. 4, that is to say from d to e in the diagram, it will be seen that the piston having passed its lower dead point, commences to rise. The crank driving the connecting rod l4 nearly occupies its highest position so that the auxiliary piston I occupies a lower dead point position, that indicated at 2B in the diagram, which is the lowest possible as at this moment the pivot I! is almost the nearest possible to the shaft 8.

When pas-sing from this new position to that in Fig. 5, that is to say from c to f in the diagram, it will be seen that when the piston 6 nearly reaches its upper dead point position, the crank driving the connecting rod 14 is in the neighbour hood of its lowest position and consequently the auxiliary piston l is in the neighborhood of its highest dead point indicated at 2! in the diagram. upper dead point is higher than the dead point l9, corresponding to the position in Fig. 3, because the pivot i! is again further from the shaft 8 than it was in the position indicated above.

'Finally when returning from the position in Fig. 5 to that in Fig. 2, that is to say from f to c on the diagram, it will be seen that the piston having passed its upper dead point, the crank 15 has completely raised the connecting rod l4, thus bringing the auxiliary piston 1 to the lower Between (-2 dead point, that indicated by 22 in the diagram. This dead point is not as low as the dead point 20 corresponding with the position of the members in Fig. 4, as in this latter position the pivot H was the nearest possible to the shaft 1 while in Fig. 2 it is on the contrary removed as far as possible,

It will be understood that the connection by a chain shown in Fig. 2 is only diagrammatic and may be replaced by any other appropriate mechanical method. In particular it is possible (see Fig. 6) to locate the pivot I! at the end of a rod 25 sliding in guides 30, and actuated by a connecting rod 26 which, at the same time as the connecting rod I4, in the example shown in Figs. 2-5, extends up to the neighborhood of the crankshaft 8, these connecting rods l4 and 26 being actuated by gearing 21 and 28 driven directly by a toothed wheel 29 of the engine shaft 8. It is therefore not necessary for the pivot I! of the tumbler to effect a rotary movement, it may equally well carry out a to and fro movement in a direction parallel to the axis of the cylinder or even inclined relatively to this axis.

Finally it may be mentioned that in passing from the position in Fig. 2 to the position in Fig. 3, that is to say from c to d in the diagram, the auxiliary piston l transmits motive force to the shaft 8 through the medium of the crank l5 and the chain I 6 or another appropriate connecting member.

I claim:

1. In an internal combustion engine, the combination with a cylinder having spaced intake and exhaust ports of main and auxiliary pistons adapted to move in said cylinder in relation to said ports and to each other, and mechanism operatively connecting said main and auxiliary pistons, said mechanism comprising a crankshaft, a'

connecting rod between said crankshaft and said piston, a tumbler pivotally mounted intermediate its ends, a link connecting one end of said tumbler to said slide, a crank disc, means operatively connecting said crank disc to said crankshaft, a link connecting said crank disc to the other end of said tumbler, and means for connecting said crank disc to the pivotal point of said tumbler, the ar-v rangement being such that the pivotal point of the tumbler is subjected to an oscillatory variation of the same frequency as the to and fro movement of the piston, so as to vary the distance between the said pivotal point and the axis of the crankshaft.

2. In an internal combustion engine, the combination with a cylinder having spaced intake and exhaust ports of main and auxiliary pistons adapted to move in said cylinder in relation to said ports and to each other, and mechanism operatively connecting said main and auxiliary pistons, said mechanism comprising a crankshaft, a connecting rod between said crankshaft and said piston, a tumbler pivotally mounted intermediate its ends, a link connecting one end of said tumbler tosaid slide, a crank disc, means operatively connecting said crank disc to said crankshaft, a link connecting said crank disc to the other end of said tumbler, and means for connecting said crank disc to the pivotal point of said tumbler, the arrangement being such that the pivotal point of iii and said crankshaft, said mechanism being such that said crank rotates at the same speed as the crankshaft.

3. In an internal combustion engine, the com bination with a cylinder having spaced intake and exhaust ports of main and auxiliary pistons adapted to move in said cylinder in relation to said ports and to each other, and mechanism operatively connecting said main and auxiliary pistons, said mechanism comprising a crankshaft, a connecting rod between said crankshaft and said piston, a tumbler pivotally mounted intermediate its ends, .a link connecting one end of said tumbler to said slide, a crank disc, means operatively connecting said crank disc to said crankshaft, a link connecting said crank disc to the other end of said tumbler, and means for connecting said crank disc to the pivotal point of said tumbler, the arrangement being such that the pivotal point of the tumbler is subjected to an oscillatory variation of the same frequency as the to and fro movement of the piston, so as to vary the distance between the said pivotal point and the axis of the crankshaft, a crank on which said tumbler is mounted, driving mechanism between said crank and said crankshaft, said mechanism being such that said crank rotates at the same speed as the crankshaft, said crank disc being driven at twice the speed of rotation of the crankshaft.

4. In an internal combustion engine, a cylinder having spaced inlet and exhaust ports, main and auxiliary pistons movable in the cylinder in relation to said ports and to each other, a lever o-peratively connected to the auxiliary piston, eccentric fulcrum means for said lever, a link for rocking said lever, eccentric fulcrum means for actuating the link and means driven by the main piston for operating respectively the said eccentric fulcrum means for the lever and said eccentric fulcrum means for the link.

5. In an internal combustion engine, a cylinder having spaced inlet and exhaust ports, a main piston movable in the cylinder, a main crank shaft therefor, an auxiliary piston also movable in the cylinder, said pistons being movable relative to said ports and to each other, a lever operatively connected with the auxiliary piston, a crank constituting the fulcrum and said lever, a link connected at one end of the lever for rocking the same, a crank pivotally connected to said link, means driven by the main crank shaft for driving the crank for the lever at the same speed as the main crankshaft, and means also driven by the main crankshaft for driving the crank for the link at twice the speed of said main crank shaft.

6. In an internal combustion engine, a cylinder having spaced exhaust and intake ports, main and auxiliary pistons respectively controlling the said exhaust and intake ports, said main piston having a constant stroke and associated with the main crankshaft of the engine, and crank, lever and link means driven by the main crankshaft for imparting a variable stroke to said auxiliary piston.

7. In an internal combustion engine, a cylinder having spaced exhaust and intake ports, main and auxiliary pistons respectively controlling the said exhaust and intake ports, said main pistons having a constant stroke and associated with the main crankshaft of the engine, and means for imparting a variable stroke to the said auxiliary piston, said means including a lever articulated on a movable pivot point controlled from the main crankshaft, and means for rocking said lever also controlled by the main crankshaft in timed sequence with the movement imparted to the lever by the main crank shaft through said articulated pivot point.

8. In an internal combustion engine, a cylinder having spaced exhaust and intake ports, main and auxiliary pistons respectively controlling said exhaust and intake ports, said main piston having a constant stroke and associated with the main crankshaft of the engine, and means for imparting a variable stroke to said auxiliary piston, said means comprising an eccentric fulcrum and means for rocking the lever on said fulcrum controlled from the said main crankshaft and whereby one of the double strokes of the auxiliary piston has an amplitude approximately half the main stroke of the main piston while the other double stroke of the auxiliary piston has a greater amplitude than the maximum stroke of the main piston.

9. In an internal combustion engine, a cylinder having exhaust and intake ports respectively controlled by main and auxiliary pistons, said main piston having a constant stroke and associated with the main crankshaft, and means for imparting a variable stroke to said auxiliary piston, whereby the said auxiliary piston performs four irregular strokes one of which is a working stroke while the main piston performs two strokes of the same amplitude, the working stroke of the auxiliary piston being such that at the dead center thereof the said auxiliary piston does not uncover the intake port which is only open after the exhaust and scavenging of the burnt gases by a following stroke of greater amplitude.

HENRI BUCHWALDER. 

